The present invention relates to an optical switch for switching optical paths of optical signals and, more particularly, to a light triggering type switch which utilizes light of a predetermined wavelength as control energy for triggering its switching operation.
With the development of fiber optic communications attention is now being paid to the optical switching technology for switching optical signals to a desired channel. It is considered, in particular, that as an optical line becomes increasingly common in the subscriber's system, optical switches will be needed in vast numbers, and their miniaturization and sophistication are desired. There is also a demand for the development of an integrated optical switching element for adaptation to submarine switching in a submarine fiber optical transmission system or satellite-loaded switch which is limited in the space therefor and required to be highly reliable.
To meet with such requirements, study is being given on an optical switch of the type in which an optical signal is once converted into an electric signal (an opto-electro conversion) and the electric signal is switched by an electronic circuit as in the past, thereafter being re-converted into an optical signal (an electro-opto conversion). As a result of the recent progress of the OEIC (Opto-Electronic Integrated Circuit) technology, a four-by-four optical switch, though in a hybrid structure, has been reported. This O/E/O type optical switch, which involves the conversion of an optical signal to electric form and then back to optical form, is readily acceptable as a miniaturized version of a conventional optical switching device formed by discrete elements. It is considered, however, that this optical switch has a defect of an increase in crosstalk by electromagnetic interference in the electronic circuit during its high-speed operation. In addition, it is difficult, at present, to obtain an ultra high-speed electronic circuit capable of performing satisfactory operations at high frequencies above several gigahertz.
Another optical switch suggested so far is one that switches an optical signal without converting it into an electric signal, and this switch is termed an O/O type.
These optical switches do not involve the O/E and E/O conversions for wide-band optical information signals, and hence has advantages that they are simple-structured and capable of switching optical signals without impairing their wide band property. These conventional optical switches are designed taking only the switching section into account and no consideration is paid to the operation for a multichannel input, that is, the operation for storing an input in a closed channel and for handling other multiplexed signals.